Zhixin Sun

A Collaborative Key Management Protocol in Ciphertext Policy Attribute-Based Encryption for Cloud Data Sharing

Ciphertext policy attribute-based encryption (CP-ABE) is a promising cryptographic technique for fine-grained access control of outsourced data in the cloud. However, some drawbacks of key management hinder the popularity of its application. One drawback in urgent need of solution is the key escrow problem. We indicate that front-end devices of clients like smart phones generally have limited privacy protection, so if private keys are entirely held by them, clients risk key exposure that is hardly noticed but inherently existed in previous research. Furthermore, enormous client decryption overhead limits the practical use of ABE. In this paper, we propose a collaborative key management protocol in CP-ABE. Our construction realizes distributed generation, issue and storage of private keys without adding any extra infrastructure. A fine-grained and immediate attribute revocation is provided for key update. The proposed collaborative mechanism effectively solves not only key escrow problem but also key exposure. Meanwhile, it helps markedly reduce client decryption overhead. A comparison with other representative CP-ABE schemes demonstrates that our scheme has somewhat better performance in terms of cloud-based outsourced data sharing on mobile devices. Finally, we provide proof of security for the proposed protocol.

Towards Secure Data Retrieval for Multi-Tenant Architecture Using Attribute-Based Key Word Search

Searchable encryption mechanism and attribute-based encryption (ABE) are two effective tools for providing fine-grained data access control in the cloud. Researchers have also taken their advantages to present searchable encryption schemes based on ABE and have achieved significant results. However, most of the existing key word search schemes based on ABE lack the properties of key exposure protection and highly efficient key updating when key leakage happens. To better tackle these problems, we present a key insulated attribute-based data retrieval scheme with key word search (KI-ABDR-KS) for multi-tenant architecture. In our scheme, a data owner can make a self-centric access policy of the encrypted data. Only when the possessing attributes match with the policy can a receiver generate a valid trapdoor and search the ciphertext. The proposed KI-ABDR-KS also provides full security protection when key exposure happens, which can minimize the damage brought by key exposure. Furthermore, the system public parameters remain unchanged during the process of key updating; this will reduce the considerable overheads brought by parameters synchronization. Finally, our KI-ABDR-KS is proven to be secure under chosen-keyword attack and achieves better efficiency compared to existing works.

Secure and Efficient Signature Scheme Based on NTRU for Mobile Payment

Mobile payment becomes more and more popular, however the traditional public-key encryption algorithm has higher requirements for hardware which is not suitable for mobile terminals of limited computing resources. In addition, these public-key encryption algorithms do not have the ability of anti-quantum computing. This paper researches public-key encryption algorithm NTRU for quantum computation through analyzing the influence of parameter q and k on the probability of generating reasonable signature value. Two methods are proposed to improve the probability of generating reasonable signature value. Firstly, increase the value of parameter q. Secondly, add the authentication condition that meet the reasonable signature requirements during the signature phase. Experimental results show that the proposed signature scheme can realize the zero leakage of the private key information of the signature value, and increase the probability of generating the reasonable signature value. It also improve rate of the signature, and avoid the invalid signature propagation in the network, but the scheme for parameter selection has certain restrictions.